/*
 *  Copyright (c) 2017 Uber Technologies, Inc. (hoodie-dev-group@uber.com)
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *           http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 *
 */

package com.uber.hoodie.common.util.queue;

import java.util.Iterator;


/**
 * Consume entries from queue and execute callback function
 */
public abstract class BoundedInMemoryQueueConsumer<I, O> {

  /**
   * API to de-queue entries to memory bounded queue
   *
   * @param queue In Memory bounded queue
   */
  public O consume(BoundedInMemoryQueue<?, I> queue) throws Exception {
    Iterator<I> iterator = queue.iterator();

    while (iterator.hasNext()) {
      consumeOneRecord(iterator.next());
    }

    // Notifies done
    finish();

    return getResult();
  }

  /**
   * Consumer One record
   */
  protected abstract void consumeOneRecord(I record);

  /**
   * Notifies implementation that we have exhausted consuming records from queue
   */
  protected abstract void finish();

  /**
   * Return result of consuming records so far
   */
  protected abstract O getResult();


}
